Mental illness (MI) ranks among the most critical health problems in the global burden of disease, and the stigma associated with it is reported to be at the center of both individual (e.g., low service use, hindered progress toward recovery) and system problems (e.g., inadequate funding of research and treatment infrastructures). In fact, studies such as the World Health Organization's International Study of Schizophrenia (ISoS) have suggested that documented differential outcomes for persons with one of the most serious forms of MI is due, in part, to the differing cultural norms, attitudes and behaviors toward persons with MI across societies. Yet, we know relatively little about whether and how the public's reaction to MI varies across countries. This application proposes the first theoretically based and methodologically coordinated attempt to understand the extent to which MI is understood and stigmatized across countries. Using a multidisciplinary and multi-level theoretical framework and a subset of International Social Survey Program (ISSP) member countries, this application proposes a 15-country, comparative study of the levels and correlates of the stigma of major depression, schizophrenia and bi-polar disorder. We propose three specific aims. First, we derive a comprehensive theoretical model of the etiology of the stigma of MI that is informed by an interdisciplinary synthesis of existing research on the causes and correlates of stigmatizing responses to persons with MI. Second, we develop and pre-test an instrument based on this framework in collaboration with an international set of mental health and survey research experts. Collected data will be from face-to-face interviews with a nationally representative sample (N=1,000-1,500) of adults in each country. This will provide national and international descriptive profiles of the public's knowledge of, familiarity with, beliefs about, and stigmatizing responses toward MI and persons with MI. Third, we empirically examine hypotheses proposed under the theoretical model, both nationally and cross-nationally. By understanding the public's reaction to different types of serious mental illness (SMI), both clinicians and researchers will be in a better position to account for the observed heterogeneity in outcomes of persons with SMI within and across countries. This knowledge can provide the scientific base for public health and treatment system interventions to mitigate the devastating negative effects of stigma on the lives of persons with SMI.